The present invention relates to a process for preparing halophenol sulfonic compounds in which the hydroxyl group, or a derivative thereof, is in the ortho position with respect to the sulfonic group. More specifically, the present invention pertains to the alkaline hydrolysis of a polyhalobenzene-sulfonate in an organic solvent which solvent directly influences the ortho orientation of the nucleophilic aromatic substitution of the hydroxyl group for a halogen atom bound to the ring in the ortho position to the sulfonic group. The halophenol sulfonic acids obtained according to the present process may optionally be desulfonated to provide halophenol compounds which are difficult to obtain by heretofore known methods.
The displacement of a halogen atom from a polyhalobenzene sulfonate by reaction with a base to obtain halophenol sulfonates is known in the prior art. Exemplary of such processes are the reaction of sodium 2,4,5-trichlorobenzene sulfonate [Journal of the American Chemical Society, Vol. 74, pages 3890-91 (1958)], sodium 2,4-dichlorobenzene sulfonate (U.S. Pat. No. 2,835,707 granted May 20, 1958), or sodium 2,3,4-trichlorobenzene sulfonate (Czechoslovakia Pat. Nos. 105,281 and 105,282 filed Dec. 5, 1960) with a base to prepare the corresponding phenolic compounds. However, in these prior art processes, the reaction was conducted in an aqueous medium and the salts of para-hydroxy chlorobenzene sulfonic acids were the primary reaction products. Moreover, in order to effectuate the desired replacement reaction according to such processes, it was necessary to conduct the reactions under extreme temperature and pressure conditions.